package com.software.cool.utils;

import com.alibaba.fastjson.JSONObject;
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.AlgorithmParameters;
import java.security.Security;
import java.util.Arrays;

/**
 * @author diaojianfeng
 * @date 2020/3/2 下午3:04
 */
public class WeixinUtils {

	/**
	 * 获取微信用户信息
	 * @param encryptedData
	 * @param sessionKey
	 * @param iv
	 * @return
	 */
	public static JSONObject getUserInfo(String encryptedData, String sessionKey, String iv){
		/**
		 * 被加密的数据
		 */
		byte[] dataByte = Base64.decode(encryptedData);
		/**
		 * 加密秘钥
		 */
		byte[] keyByte = Base64.decode(sessionKey);
		/**
		 * 偏移量
		 */
		byte[] ivByte = Base64.decode(iv);

		try {
			/**
			 * 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
			 */
			int base = 16;
			if (keyByte.length % base != 0) {
				int groups = keyByte.length / base + (keyByte.length % base != 0 ? 1 : 0);
				byte[] temp = new byte[groups * base];
				Arrays.fill(temp, (byte) 0);
				System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
				keyByte = temp;
			}
			/**
			 * 初始化
			 */
			Security.addProvider(new BouncyCastleProvider());
			Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding","BC");
			SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
			AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");
			parameters.init(new IvParameterSpec(ivByte));
			/**
			 * 初始化
			 */
			cipher.init(Cipher.DECRYPT_MODE, spec, parameters);
			byte[] resultByte = cipher.doFinal(dataByte);
			if (null != resultByte && resultByte.length > 0) {
				String result = new String(resultByte, "UTF-8");
				return JSONObject.parseObject(result);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}
}